Such automatic biochemical analyzers for analyzing biological samples have been known, as proposed in Japanese Patent Laid-Open No. 2024/1993. In this prior art technique, a plurality of sample containers are set on a sample disk. In this instrument, aliquots or sample in the sample containers set on the sample disk are drawn in by a sample pipette and dispensed into reaction containers on a reaction disk. A reagent pipette draws in reagents from plural reagent disks and adds the reagents to the aliquots of sample. Thus, the sample is analyzed in terms of plural items. During the analysis, the order in which the items are analyzed is determined, taking account of the time required for the processing, in order to shorten this processing time.
Where an aliquot of sample or reagent is injected by a pipette, a given amount of sample or reagent is aspirated while a portion of the pipette on the side of the front end is dipped in a sample or reagent held in a container. Then, the pipette is moved to a reaction container while the aliquot of sample or reagent is kept aspirated. Finally, the aliquot is injected into the reaction container. When the front end portion of the pipette is moved out of the container, a part of the aliquot of sample or reagent adheres to the outer surface of the front end portion of the pipette and remains there. Where a part of the aliquot of sample or reagent remains inside or outside the pipette in this way, if the next aliquot of sample or reagent is injected by the same pipette, various problems take place.
Accordingly, it is customary to wash the inner and outer surfaces of the pipette when the injection of one aliquot of sample or reagent ends. In the prior art technique, wash water is sprinkled on the outer surface to wash it. To wash the interior of the pipette, a given amount of wash water is drawn into the pipette, and then the drawn water is drained off.
However, if wash water is simply showered on the outer surface of the pipette, the wash water is not quickly discharged and thus a part of the wash water remains on the outer surface of the pipette. If a new sample is subsequently injected, the factor by which the sample is diluted may deviate from the intended value. If a reagent is aspirated, the concentration of the reagent may deviate from the intended value. Consequently, it is difficult to obtain accurate measurement results.